Mechanism of action of bacitracinbacitracin is an antibiotic produced by the strain of bacillus subtilis. it acts by inhibiting bacterial cell wall synthesis. it is active against a variety of gram positive and a few gram negative organisms.mechanism of action of neomycinaminoglycosides like neomycin "irreversibly" bind to specific 30s-subunit proteins and 16s rrna. specifically neomycin binds to four nucleotides of 16s rrna and a single amino acid of protein s12. this interferes with decoding site in the vicinity of nucleotide 1400 in 16s rrna of 30s subunit.mechanism of action of polymyxin bpolymyxin b sulfate has a bactericidal action against almost all gram-negative bacilli except the proteus group. polymyxin b sulfate interacts with the lipopolysaccharide of the cytoplasmic outer membrane of gram-negative bacteria, altering membrane permeability and causing cell death. it does not need to enter the cell.